Control of the unsaturated nature of membranes resides largely within a group of enzymes known as the acyl-CoA desaturases. There are three, possibly four, desaturase enzymes located in the endoplasmic reticulum. The desaturases do not function alone but require the presence of NADH cytochrome b5 and a lipid membrane. Dietary changes have been shown to induce the Delta 9, Delta 6 and Delta 5 desaturase. High carbohydrate, low-fat diets induce the Delta 9 desaturase; high protein diets induce the Delta 6 desaturase; and diets high in oleic acid induce the Delta 5 desaturase. We have observed ethanol to prevent the acute induction of the Delta 9 desaturase in a diet high in carbohydrate and low in fat, and we have observed chronic ethanol ingestion to result in decreased activities of all three desaturases. By studying the three desaturases under conditions which have been shown to induce their activity, by using rats of differing ages and by using purified components of the desaturase systems, and by using their antibodies, we hope to show that ethanol ingestion exerts its influence by inhibiting the synthesis of these desaturase proteins. By further study of the purified enzymes involved with desaturation, we hope to better understand the effects of ethanol on protein-protein interactions in membranes. This information will provide the ground-work data for further study into the mechanisms by which ethanol produces tolerance and dependence.